The World of Microbes Class 4 - Questions and Answers

The World Of Microbes

Microbes are small living things that can be found almost anywhere on Earth. They include bacteria, viruses, fungi, and protozoa. While some microbes are beneficial, such as those that help us digest food or break down dead organic matter, others can cause illnesses or infections. For example, some bacteria can cause food poisoning, while viruses can cause diseases like the flu. It's important to remember that not all microbes are harmful, and many are necessary for life on Earth. Practicing good hygiene, such as washing your hands regularly, can help prevent the spread of harmful microbes and keep us healthy.

Time To Revise

[tikbox]We can see microbes only through a powerful microscope.
[tikbox]Microbes are of four types-bacterium, virus, fungus and protozoa.
[tikbox]Some microbes are useful while others are harmful.
[tikbox]Useful microbes help us in many ways.
[tikbox]Harmful microbes cause several types of diseases.

1. Answer the following questions.

1. What are microbes?

Ans. Microbes are tiny living things that are found in air, water, soil and even inside our body.

2. How do microbes help us?

Ans. Some microbes are very useful to us
i) Bacteria Convert milk into curd..
i) Yeast makes bread and idli soft and fluffy.
iii) Some bacteria present in our stomach help in digestion of food.
iv) Some microbes are used to make medicines.
eg. Penicillin is made from fungus "Penicillium".
v) Some bacteria also produce vitamins in our body.

3 Differentiate between virus and protozoa.

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Virus	Protozoa
i) A virus is smaller than bacteria. It is found everywhere.	Protozoa are tiny single celled organisms. They live in water, soil and also inside the human body.
ii) It causes diseases like common cold, chicken pox, polio, etc.	ii) It causes diseases like malaria and dysentery.

4. Name some diseases which are caused by protozoa, bacteria and fungi.

Ans i) Diseases caused by protozoa - Malaria -Dysentery
ii) Diseases caused by bacteria - Typhoid - pneumonia
ii) Diseases caused by fungi - Skin diseases, Food poisoning.

5. How do doctors sterilize their instruments?

Ans. Doctors sterilize their instruments by heating them in a specific way to kill germs before an operation.

Which bacteria is present in curd?

Ans: The bacteria present in curd are primarily lactic acid bacteria. The two main types of bacteria involved in the fermentation of milk to produce curd are:
Lactobacillus bulgaricus: This bacterium is responsible for the initial stages of fermentation and contributes to the characteristic flavor of yogurt or curd.
Streptococcus thermophilus: This bacterium works in conjunction with Lactobacillus bulgaricus to ferment lactose (milk sugar) into lactic acid, which thickens and acidifies the milk, leading to the formation of curd.
These bacteria help in the digestion of lactose, produce certain vitamins, and contribute to the overall health of the digestive tract.

Answer the following questions

Answer in one word:
1. The microbes which split to reproduce. - Bacteria
2. Heating instruments before an operation. - Sterilisation
3. The tiny one-celled organisms that cause chicken pox.. Virus
4 . Medicines which are used on wounds to prevent infection - Antiseptics
5. Microorganisms that cause common cold. - Virus

Column - A	Column - B
Bacteria Virus Protozoa Fungi	Tuberculosis Common cold Skin disease Malaria

1. We can preserve foods by dehydrating. [T]
2. Penicillin is made from a virus. [F]
3. Protozoa is a single-celled organism. [T]
4. Bacteria turn milk into curd [T]
5. All germs are not microbes [T]

Think and answer:

I help to make bread. I can be seen only through a microscope. Who am I? Fungus
I live in human blood and mosquito. I cause malaria. Identify me. - Protozoa
I am smaller than bacteria. I cause common cold. Who am I? Virus.